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HOMESERVICE MANUALSEAGLE1990PREMIER ESREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCETESTING & DIAGNOSISENGINE CONTROLS - SYSTEM/COMPONENT TESTSCONTROL UNIT HARNESS TEST
1990 Eagle Premier ES

Control Unit Harness Test

1990 Eagle Premier ESSECTION Control Unit Harness Test
  1. If during G - TESTS W/CODE testing Electronic Control Unit (ECU) is found to be faulty, perform the following steps to ensure ECU is faulty.
  2. Most components are incorrectly diagnosed due to faulty electrical connectors or poor connections between component and vehicle.
  3. Sometimes, simply disconnecting and connecting an electrical component will provide a good electrical connection. Before replacing an ECU, check all components in suspect circuit. If components are okay, carefully disconnect ECU from vehicle harness.
  4. Inspect ECU harness connector and ECU contact pins for corrosion. Clean harness connector and ECU contact pins with contact cleaner.
  5. Inspect ECU harness connector for bent pins, missing pins and broken wires. Repair or replace as necessary.
  6. Connect ECU harness connector to ECU and retest system with Diagnostic Readout Box (DRB-II) and Jeep/Eagle adapter or similar scan tool. See appropriate TESTS W/CODES article. If vehicle does not pass test and fails with same message, replace ECU.
RENDER: 1.0x

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.